The present disclosure relates to a light emitting device, a light emitting device package, and a lighting system.
Light emitting devices based on a nitride semiconductor thin film convert electric energy into light energy. With the development of thin-film growth techniques and light emitting materials, light emitting devices, using a nitride semiconductor material which is formed by combining the group III element and group V element of the periodic table, emit white light having various wavelengths (colors) such as red, green, blue, and ultraviolet light, and realize high efficient white light by using fluorescent materials or combining colors. Moreover, light emitting devices based on a nitride semiconductor thin film have low power consumption, semipermanent life, fast response time, stability, and environmental friendliness compared to the existing light sources such as fluorescent lamps and incandescent lamps. Therefore, the application of light emitting devices are being expanded to Light Emitting Diode (LED) backlights that replace Cold Cathode Fluorescent Lamps (CCFLs) configuring the backlight unit of a Liquid Crystal Display (LCD) device, white LED lighting devices for replacing fluorescent lamps or incandescent bulbs, the head lights of vehicles, traffic lights, etc. In expanding the application of nitride semiconductor light emitting devices, technology for developing high efficient light emitting devices is fundamentally required.
Nitride semiconductor light emitting devices of the related art have a limitation in that light emission efficiency is reduced due to a serious nonradiative recombination loss process when a high current is injected. The cause is not clearly established, and many global scholars and experts are actively researching for finding the cause. Also, nitride semiconductor light emitting devices of the related art have a limitation in that light emission efficiency is reduced by a nonradiative recombination loss process due to a crystal defect when a low current is injected.
In nitride semiconductor light emitting devices emitting blue light and green light, the reduction in light emission efficiency that is caused when injecting a high current is one of urgent technical limitations in implementing light emitting devices for high output and high efficient lighting.
Consequently, it is acutely being required to develop ideal nitride semiconductor light emitting device structures that provide excellent light emitting quantum efficiency in all injection current regions ranging from a region having the low amount of injection current to a region having the high amount of injection current.